Signal seek tuner



March 3, 1959 D. BIRX SIGNAL SEEK TUNER Filed April 28, 1954 FIG.

MR T v m8 V. mL D N w 0 D B ATTORNEYS United SIGNAL SEEK TUNER Donald L.Birx, Havertown, Pa, assignor to Radio Contlenser Company, Camden, N.3., a corporation of New Jersey Application April 28, 1954, Serial No.426,237

2 Claims. (Cl. 250-) This invention relates to signal seek tuners of thetype used in radio or television receivers in which changes fromreception of one transmitting station to another are effected by themomentary depression or movement of a push button or the like.

Signal seeking tuners of the type which provide variation of positionsof tuning elements upon initiation by signal seeking buttons, or thelike, usually involve rotary motor drives, the motors being driven fromD. C. batteries which, in the usual automotive use of such tuners, wouldbe the ordinary car batteries. Such motors drive the tuning elements,usually at the present time tuning inductor cores, through connectionsincluding reduction gearing. Since it is desired to stop the tuningoperation precisely when tuning is eliected to an incoming signal, ithas generally been necessary not only to provide a clutch fordisconnecting the motor but also a brake for stopping the parts of theconnections directly associated with the tuning elements. Manyvariations of the foregoing have been proposed but in common they havethe disadvantages of both mechanical and electrical complexity and, inparticular, the necessity for utilizing relays for the iu terl'uption ofdrive by the motor and the application of brakes. Mostof thecomplications may be ascribed to the inertia of the driving motor partsand the necessity for eliminating the efiects of this inertia insecuring sharp tuning.

in the application of I. C. Heselwood, Serial No. 426,222, filed April28, 1954, there is described and claimed a type of motor which isparticularly advantageous in its application to signal seek tuners. inbrief, and as will appear more fully hereafter, a vibrating drivingmeans drives through a gripping pawl a movable member which may have astraight line or rotary movement. The amplitude of the vibration and theaccompanying step imparted in each-cycle to the driven member are bothvery small. However, quite rapid advance may be secured by increasingthe frequency of vibration. A gripping dete'nt prevents retrogrademovement of the driven member.

During active operation, the movement of the driven member isintermittent and, consequently, it comes to rest in each cycle of thevibration if the mass of it and its associated parts is reasonably lowas may be the case in a signal seek tuner and its movement is opposed,for example, by spring action. Consequently, assuming that the drivingvibration may be interrupted within a single cycle, it is capable ofbeing positioned within the limit of a single step of movement.

An advantageous aspect of this motor is that it involves anelectromagnetic vibrator having. an armature associated with analternating field With provision for providing either a polarized ornonpolarized condition of the armature. The polarization isaccomplishedby a direct current which does not provide the major driving energy and,hence, may come from a source having a quite low power output such asthe direct current supply for a radio. The power input for effectingdrive is alternating and the i atented Mar. .3, 1959 alternating supplymay be permanently connected to the driving arrangement without thenecessity for switching, there being no vibration occurring when thearmature is unpolarized. The control for effecting stopping and startingof the motor being a low power direct current, there is not required anypower reiay for this control and, as will appear, the control may bequite simply effected.

The objects of the invention are concerned with the provision of asignal seek tuning arrangement particularly adapted to the type of motorjust indicated. When the motor is of a linear type, effecting movementofa driven member in a straight line, provision is made for the automaticrestoration of the driven member to initial position at the end of itsdriven movement so as to effect repeated, though interrupted, scanningof a predetermined frequency band of a receiver. These objects'willbecome more apparent from the following description, read in conjunctionwith the accompanying drawing, in which:

Figure 1 is a diagram illustrating the signal seeking radio receiverincorporating the matters of the invention;

Figure 2 is an enlarged fragmentary sectional view showing details ofthe gripping pawl and detent arrangements of the driving motor; and

Figure 3 is a fragmentary diagram showing the type of motor which may beused for rotary drive of tuning condensers or the like.

The signal seeking tuner in accordance with the inv'ention has, from thestandpoint of an operator, very much the same characteristics as signalseeking tuners presently known: i. e., if it is desired to change fromreception of one transmitting station to another, there is a momentaryoperation of a push button or the equivalent whereupon the tuner seeks anew signal, stopping thereon for proper tuning. In accordance with theinvention, this general end is accomplished in novel and advantageousfashion as will presently appear.

The receiver may be of any desired type but is indicated as aconventional superheterodyne receiver comprising a radio frequencyamplifier 2, a converter 4 which comprises an oscillator and a mixer, anintermediate frequency amplifier 6, a detector 3, an audio frequencyamplifier lid and a speaker 12. it may be assumed that tuning of thereceiver is effected through variation of inductors by movement of coresand in Figure l the coils of these inductors are indicated at M, 16 and18 andthe respective movable cores at 2%, 22 and 2d. The inductors may,respectively, be provided as usual in the radio frequency amplifier, theoscillator and mixer. The cores 2t 22 and 24 are secured to, and movablesimultaneously by, a common member as which is connected to a rodZSwhich may be guided for straight line movement through any suitablemounting means 3%.

To provide control for automatic stopping of the tuning on a signal,there is provided a frequency discriminator 32, receiving the output ofthe intermediate frequency amplifier 6, and which will be recognized asof generally conventional type comprising a pair of circuits tuned tothe intermediate frequency of the receiver and pro viding through diodes34 and 36 a direct output through the filter 38 which will vary withrespect to ground from a substantially negative value through zero to apositive value as tuning passes through the frequency of a receivedstation. The connection 33 runs to the control grid of thyratron 40 thecathode of which is connected to the adjustable contact of potentiometer42 in a resistance array which, as will appear, is at times connectedbetween a point or" positive potential and ground so that which in thecase of automotive use would be of vibrator type receiving power fromthe automobile battery and supplying high voltage alternating currentrectified to provide at terminal 46 the high voltage direct current forthe operation of the radio receiver. For the purpose of operating thetuning motor the high voltage alternating current terminals of the powersupply are tapped to provide an alternating current output betweenterminals 48 and 50.

Terminal 52 is connected to the positive supply terminal 46. Associatedterminal 54 is connected to the resistance arrangement including thepotentiometer 42 and also to a contact terminal 56 of relay 58 themovable contact 60 of which is connected to the terminal 46. One end ofthe winding of relay 58 is connected to ground through winding 59 of themotor, to which winding reference will be hereafter made. The other endof the winding 58 is connected through a pair of resistances 62 and 64to the terminal 54 and the junction of these resistances is connected toa terminal 66. A ter minal 68 is connected to the anode of thyratron 48.A push button switch 70 is provided which, when released, is spring-heldto connect terminals 66 and 68. When manually pressed, the switch opensthe connection between terminals 66 and 68 and closes a connectionbetween terminals 52 and 54.

In its preferred form the motor comprises a laminated core 72 which isprovided with a gap 74 across which an alternating magnetic field isprovided by reason of the location on the core 72 of an alternatingcurrent winding 76 the ends of which are connected to the alternatingsupply terminals 48 and 50. Condenser 78 desirably shunts the winding 76to provide approximate tuning to the frequency of the alternatingsupply.

Armature 80 is pivoted at 82 to the core 72 in mag netic contact withthe core and projects through the gap 74. The winding 59 previouslymentionel surrounds the armature 80.

Springs 84 urge the rod 28 and the cores 20, 22 and 24 in upwarddirection as viewed in Figures 1 and 2. Lever 86 is pivoted at 88 to themotor assembly frame, which may have any convenient form and is notshown, and is urged downwardly by a spring 90. A pin 92 carried by lever86 is held by a hook on the lever 94 which is pivoted to the frame at 96and is provided with an arm 98 extending across the bar 28. A spring 100normally urges the lever 94 toward a clockwise position to provideretention of the pin 92.

A gripping pawl 102 is provided in the form of a small block and asimilar block provides a gripping detent 104. The right-hand end of thepawl 102 is pressed upwardly by leaf spring 106 which is secured to thelever 86. The left-hand end of the pawl 102 has its upper surfaceengaged by the end of the armature 80.

The upper side of the left-hand end of detent 104 engages pin 108 fixedin the frame while its right-hand end is engaged and urged upwardly byleaf spring 110 secured to the lever 86.

The pawl 102 and detent 104 are, respectively, provided with openings114 and 116 which have cross-sections corresponding to the rod 28 (whichmay be circular or rectangular) but are slightly larger to provideclearance for the passage of the rod, and, at the same time, for atilting and gripping action as will be clear from Figure 2.Consideration of Figure 2 will make clear that if the left-hand end ofpawl 102 is moved downwardly by armature 80, a gripping action willoccur on the rod 28 so that the rod will be moved downwardly, thegripping action being insured by the action of the leaf spring 106 atthe right-hand end of the pawl. During such downward movement, thedetent 104 will be rocked slightly clockwise whereupon a slightclearance is provided to permit the downward movement of the rod. At theend of such enforced downward movement the rod will tend to moveupwardly under the action of springs 84. Such movement is prevented,however,

by the detent 104 which is backed up by the pin 108 and held in positionto effect gripping by the leaf spring 110. As the end of the armature 80moves upwardly, the pawl 102 may follow it under the action of leafspring 106 and, consequently, the pawl 102 moves upwardly relative tothe rod 28 to assume a new position for gripping it to drive itsubsequently downwardly.

Continuing the description of the parts, the lever 86 is provided withprojections 118 and 120 which are in position to engage the right-handends of pawl 102 and detent 104 when the lever 86 isreleased. Downwardmovement of the lever 86 is limited by the fixed pin 122 which pin,together with a second fixed pin 124, serves to provide guidance for therod 28 in addition to such guidance as may be afforded at 30.

Pin 126 is carried by the upper end of the rod 128 and is arranged toengage the extension 98 of lever 94 at the end of travel of the rod 28.Pin 128 carried by the rod is arranged to engage the left-hand lower endof the lever 86 when the rod 28 moves upwardly.

A contact 129 is arranged to be engaged by lever 86, which iselectrically grounded, when lever 86 is released by latch 94. Contact129 is connected through line 131 to the input of the I. F. amplifier 6which is accordingly grounded when the lever 86 is released to interruptsignals through the receiver and in particular to interrupt signals tothe discriminator.

The parts having been described, the overall operation of the system maynow be outlined.

Assuming that the radio has been tuned to a station, there will beprovided at connection 38 a positive potential, the discriminatorcircuit being so tuned that the change from a negative to positivepotential at this connection occurs at a frequency slightly below thecenter of the intermediate frequency band pass. The contacts at 56 andwill be open and the push button switch will occupy the left-handposition illustrated with the result that there is no anode potentialapplied to the thyratron 40 and, furthermore, no current flows throughthe winding 59. Accordingly, the armature is unpolarized and it is,therefore, unmoved by the alternating field across the gap 74 providedby the winding 76 which is permanently connected to the alternatingsupply terminals 48 and 50. The rod 28 is held against the action ofsprings 84 by detent 104 and latching lever 94 engages pin 92 to holdlever 86 in the position illustrated. The tuning condition effected bythe cores 20, 22 and 24 is thus maintained.

If it is desired to tune the receiver to another station, the pushbutton switch 70 is manually pressed to the righthand positionillustrated and then released. Depression of this switch disconnects theterminals 66 and 68 and connects the terminals 52 and 54. The connectionof terminals 52 and 54 provides a positive potential to the right-handend of resistance 64 and, consequently, provides direct current flowthrough the relay Winding 58 and the motor winding 59. The energizationof the relay closes the contacts 56 and 60 and the circuit therethroughprovides the positive potential to the terminal 54 despite the openingof the connection between 52 and 54. When the switch 70 is released,connection is provided between terminals 66 and 68 so that there isapplied to the anode of the thyratron 40 the positive potential existingat the junction of resistances 62 and 64. Even if the push button 70 ispressed and almost immediately released, movement of the rod 28 willhave been initiated to tune the receiver off the signal frequency and,consequently, the potential at 38 will have dropped to a non-firingpotential considering the fact that, though a positive potential isapplied to the anode of the thyratron, its cathode also has a positivepotential due to its connection to the potentiometer 42 and the positivepotential existing between terminal 54 and ground applied to theresistance array including the potentiometer. The thyratron,accordingly, remains in unfired conditionfollowingrelease of the pushbutton switch.

germane:

The direct current fiowthrough winding: 59' provides movement impartedto the rod 28' in each cycle may be of the order of a thousandth of aninch. The frequency of vibration, however, is such that average movementof the rod 28 is reasonably fast. By control of the currents flowing,both direct and alternating, initial adjustments of the average rat'e'ofmovement may be readily made to suit desired operating conditions.

It. may be here noted that when the direct current polarization of thearmature is removed the alternating current flow through the coil 76 isvery substantially reduced thus lowering the drain on the power supplyand preventing overheating.

The intermittent movement of the rod 28 downwardly then continues untiltuning to another signal of sufiicient strength to effect control isapproached. The incoming signal first produces a negative potential at38. As precise tuning is approached, this potential passes through zeroand becomes positive. The rate of change of this potential with theincoming frequency depends upon the amplitude of the signal and theparameters of the discriminator circuit are desirably chosen or adjustedso that the potential at 38 becomes sufficiently positive to fire thethyratron 40 just as the tuning of the receiver reaches the frequency ofan incoming signal. It may be here noted that by adjustment of thecontact of potentiometer 42 selection may be afforded between signalswhich are relatively strong and relatively weak so that the operator mayset the sensitivity either to pick up any weak signals or to pick uponly relatively strong signals as may be received from, for example,local transmitting stations. When the potential at 38 reaches a firingpotential, firing of the thyratron 40 occurs with the result that itsanode potential drops close to its cathode potential providing acorresponding drop of potential at the junction of resist ances 62 and64 to cause the current through the relay 58 to be insufficient tomaintain closed the contacts 56 and 60. Accordingly, these open with theresult that the sup ply potential is removed from terminal 54, removingthe anode potential of the thyratron and eliminating current fiowthrough relay 58 and winding 59. The armature 80 is, accordingly,unpolarized and, consequently, its vibratory movements stop, leaving therod 28 in the attained position corresponding to tuning to the signalsof another transmitter. In fact, the interruption of vibration ofarmature 80 is not dependent upon the opening of the relay contacts, thedrop of potential at the junction of resistances 62 and 64 upon firingof the thyratron reducing the polarization of the armature to suchextent that its vibratory amplitude is so small that little or nomovement is imparted to rod 28. Therefore, even if the opening ofcontacts 56 and 60 is delayed, the motion of 28 is very sharplyarrested, within the period of one cycle of the alternating supply.Extremely accurate positioning for tuning is thus assured. With thecircuit described stopping on signal is accurately effected irrespectiveof large variations of signal strength so long as the adjustment atpotentiometer 42 is such as to effect stopping on the weakest signals tobe detected.

The foregoing operations may be repeated to secure tuning across theentire frequency band of the receiver. As the end of the tuning range isreached, the pin 126 engages the extension 98 of lever 94, releasing thepin 92 so that the lever 86 is rocked counterclockwise against stop 122by spring 90. The projections 118 and 120 then press downwardly theright-hand ends of pawl 102 and detent' 104from'which springs 1116 and110 have been re moved by the movement of lever 86 and therod 28 thusfreed to' be moved upwardly by the springs 84. T he'- upward. movementoccurs quickly and at its upper limit the pin 128 engages the lowerleft-hand end of lever 86, snappingv this lever upwardly against theaction of spring 90 to lift the pin 92 above the hook end of lever 94 bywhich it will be engaged and thereafter held since theextension 98 willpreviously have been released by pin 126.-

The actions of the pawl and detent are thus reinstated and if at the endof this movement a received signal has not been tuned, the automatictuning action will continue until tuning of an incoming signal isachieved as prevlousv ly described.

When the lever 86 is rocked by spring upon release of detent 94,.contact129'is grounded and signals through the'receiver to the discriminatorare interrupted until the contact at 129 is reopened by the rocking oflever 86 by pin 128. Thus a complete return of therod 28 is insuredbefore the discriminator action may again become eifec= tive. This alsoprevents noise output from the speaker as the setis reversely tunedthrough stations.

From the foregoing. it will be seen that there is provided in accordancewith the invention a sharp tuning action involving control of only verylow power and Without the necessity for providing brakes to preventoverrun of the tuning elements.

The invention is also applicable to the signal seek tuning of a receiverof a type involving rotary adjustments of ganged condensers or otherdevices such as may be used in ultra high frequency receivers. Directrotary operation may be secured without the necessity for involvement ofgearing or other means for transforming a linear motion to a rotary one.The type of motor arrangement for this purpose is illustrated in Figure3 wherein 130 indicates a rotary member which may drive directly themovable plates of tuning condensers in a radio or television receiver,or the like, or rotary elements involved in line tuners, or the like,for ultra high frequency use. The rotary member 130 is provided with arim 132 which may be of rectangular cross-section and there is provideda driving pawl 134 corresponding to 102 previously described but takingthe form of a slotted member embracing the rim with a slight clearance.The pawl is engageable by the projection 138 of armature 140 pivoted at142 and located between the poles 144 and 146 of a laminated core whichis also provided with a central portion 148 closely approaching thearmature 140. An alternating current winding 150 is provided on theouter legs of the core while the central portion thereof is providedwith a direct current winding 152.

Detent 156, similar in structure to the pawl 134, embraces the rim 132and engages a fixed pin 158. Springs 154 and engage, respectively, thepawl 134 and detent 156 and correspond to the springs 106 and 110previously described. Assuming a 360 rotary movement, there is nonecessity for providing releasing means such as the lever 86 previouslydescribed. It will be evident that the arrangement illustrated in Figure3 operates in the same fashion as that illustrated in Figure 1,vibration of the armature occurring only when the direct current coil152 is energized despite the fact that the alternating current coil maybe continuously energized.

It may be here noted that various winding arrangements and physicalarrangements of the vibrating driving means may be provided. Forexample, the alternating and direct current windings may be interchangedin both Figures 1 and 3.

It will be clear that numerous variations may be made in the specificembodiments of the invention without departing from the scope thereof asdefined in the following claims.

What is claimed is:

l. A radio receiver of signal seek type comprising variable signaltuning means, a motor for driving said tuning mamas means, said motorcomprising a field member providing a gap, at vibratory member having aportion located in said gap, a winding for said field member, a windingfor said vibratory member, means providing alternating current throughone of said windings and direct current through the other, a movabledriven member connected to said variable tuning means to adjust thelatter, frictional gripping means movable by vibration of said vibratingmember to advance said driven member, detent means prevent ing backwardmovement of said driven member, and means for interrupting said directcurrent when said tuning means attains positions tuning receivedsignals.

2. A radio receiver of signal seek type comprising variable signaltuning means, a motor for driving said tuning means, said motorcomprising a field member providing a gap, a vibratory member having aportion located in said gap, a winding for said field member, a windingfor said vibratory member, means providing alternating current throughone of said windings and direct current through the other, a movabledriven member connected to said variable tuning means to adjust thelatter, frictional gripping means movable by vibration of said vibratorymember to advance said driven member, detent means preventing backwardmovement of said driven member, means for interrupting said directcurrent when said tuning means attains positions tuning receivedsignals, spring means urging said driven member backwardly towards aninitial position, means operated by said driven member upon itsattainment of a predetermined forward position to release it from saidgripping means and said detent means for backward movement to saidinitial position under the action of said spring means, and meansefiecting reengagement of said driven member by said gripping means andsaid detent upon the attainment by said driven member of its initialposition, thereby to effect resumption of its advance.

References Cited in the file of this patent UNITED STATES PATENTS825,877 Boucherot July 10, 1906 2,056,200 Lowell Oct. 6, 1936 2,323,441Baird July 6, 1943 2,499,573 Dunn Mar. 7, 1950 2,511,580 Goodrich June13, 1950 2,565,876 Nicholson Aug. 28, 1951 2,606,222 Clifford Aug. 5,1952

